The advent of light emitting diode (LED) based luminaires has provided sports arenas, stadiums, other entertainment facilities and other commercial and industrial facilities the ability to achieve instant on-off capabilities, intelligent controls and adjustability while delivering excellent light quality, consistent light output and improved energy efficiency. Because of this, users continue to seek improvements in LED lighting devices. For example, new and improved ways to direct light in multiple directions, and maintenance of certain characteristics of light such as intensity or color temperature, are desired. However, accurate control has been limited because of the manual operation required to change colors, intensities, and positions associated with overhead light fixtures.
White light sources that use LEDs in their construction can have two basic configurations. In one, referred to as direct emission LEDs, white light is generated by direct emission of different colored LEDs. Examples include a combination of a red LED, a green LED, and a blue LED in a surface mounted device (SMD) LED. The other basic configuration includes a phosphor-based single LED that generates a beam in a narrow range of wavelengths, which impinges upon and excites a phosphor material to produce visible light. Typically, the LED die or chip generates blue light in the visible part of the spectrum and the phosphor re-emits yellow or a combination of green and red light, green and yellow or yellow and red light. The portion of the visible blue light generated by the LED which is not absorbed by the phosphor mixes with the yellow light emitted to provide light which is perceived by the human eye as being white in color. The color temperature of an LED is determined by the phosphor composition incorporated in the LED. Advantages of phosphor based LEDs over direct emission white LEDs include better color stability as a function of device aging and temperature, and better batch-to-batch and device-to-device color uniformity/repeatability.
Color tuning of LEDs, especially direct emission white LEDs, can be difficult to implement. Chip-on-board (COB) LEDs include multiple die (typically 9 or more) that are wired to operate as one electrical device and assembled with a single optical emitting surface, and hence require multiple channels to adjust individual levels of light output to create color changing effects.
Beam control in COB LEDs is also difficult. Typically, an LED lighting device is designed to provide a fixed beam pattern and spread using diffusers, total internal reflection (TIR) optics and/or collimators. If a particular light fixture is designed to provide a “wide” beam, the fixture generally cannot be adjusted easily to produce a “narrow” beam. Typically, changing the beam pattern requires changing the lighting device itself, providing a lighting device with motor-controlled movement, or manually adjusting one or more structural features of the lighting device's housing.
When there are multiple COB LEDs under a single optical source (lens), the high number of LEDs and complexity of optical and electrical components makes color tuning and beam control even more difficult.
This document describes new lighting devices that are directed to solving the issues described above, and/or other problems.